R

RonRV8

Member
When you do a full power departure stall, if you do not recover when you get the first buffet, but instead let the airplane break, does your engine sputter or lose power for a moment when you fall through until you get flying speed and can reestablish a climb?
 
Not with mine. First off, it is almost impossible to do a full power stall. At mid-weight, it doesn't happen. I can show 0 airspeed and 700fpm climb with the rudder almost full right, full back stick and no break. Backing off the power a bit, or at full gross, it will stall but the engine has never stumbled. If yours does miss, you might try it with the electric FP on. At least on the 9A, you are so steep that it may take the electric FP just to get fuel to the carb. Just a thought...

Bob Kelly
 
No noticeable problem

The -8A I fly has the O-320H2AD engine withe 4SPA carb --- no problem with stalls or in any other configuration.
 
RonRV8 said:
When you do a full power departure stall, if you do not recover when you get the first buffet, but instead let the airplane break, does your engine sputter or lose power for a moment when you fall through until you get flying speed and can reestablish a climb?
Click to expand...

Nope, not mine!
 
G- Forces

Are you by any chance experiencing zero or slight negative "G" when you initiate the recovery? If so, you might experience a momentary engine stumble or hesitation.

Think of it this way: If you are getting "light" in the seat, so is the fuel in the carb, and the float in the carb. If the carb float rises, it shuts off the fuel going to the engine. Engine stumbles, or if the negative G is a bit prolonged, the engine quits until positive G is restored, then it runs just fine.

Try doing the stall recovery with a bit less forward stick, and see what happens.

$0.02
 
not on mine either

Bob is right, it's hard to get a sharp departure stall break on mine with full power. Hangs on the prop with stick full back. At full gross it will break sharper at full power, but I have never gotten any engine stumble. I always have the aux pump on when doing stalls and such.

Regards,
Chris
 
More background on this question

Thanks for the feedback. If anyone who has had their RV-8 engine stumble in a departure stall I would like to hear from you.

When doing the departure stall with full power in my RV-8, I always have the fuel pump on, and the fuel pressure stays steady at 5 psi., the nose pitches down after the break and that is when the engine coughs, stumbles or momentarily cuts out. I do not push the stick forward, but ease the back pressure to allow the nose to lower to a deck angle that will allow a prompt stall recovery. I am a reasonably experienced pilot (almost 1,000 hours) in various single engine airplanes including Cessna 150, 172, 182, Piper Cherokees (which will not properly stall) Citabria, and Cub, but I have never had a plane with this issue. I have had two different experienced instructors ride with me during the departure stall in this airplane, and both have commented that I need to find the problem.

I have had two different shops try to solve this problem. They did fuel flow test, checked the mags, and inspected everything that they could think of. The second shop replaced the carburetor and the problem persists.

I do feel light when the airplane breaks in the stall, but the G meter stays positive, +0.6. The engine (O-320 H2AD with “T” mod. and 9.5 Barrett flow matched cylinders) runs great except for this issue. I am looking for ideas.

Thanks for the suggestions.

Ron Brestel
Marshahalltown, Iowa
 
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